8: ectosymbiosis Flashcards
what are the 3 types of ectosymbiotic behavioural mutualisms?
ant plant
ant aphid
pollination
what is the basic overview of the acacia P.ferruginea mutualism?
plant provides ant with shelter and food in return ant can defend plant from herbivore attack
list 3 plant specialist adaptations to deal with ant plant mutualism
- energy rich beltian body
- modified thorn domatia
- extra floral nectaries
what are energy rich beltian bodies?
yellow fatty deposits on leaves that ant take to raise larvae
what are domatia?
swollen body around thorns that ants use for nesting
ant-plant mutualism has evolved many times but in how many genera?
100
explain the example of Chamaecrista nectaries
they exude sugar via holes direct to the phloem
produced on leaves and stems
what did Baker-Meio et al 2012 do and discover about EFN?
- removed some EFN and kept some present
- measured proportion of successful fruits host plants produced
- when no nectaries less successful fruit
- tested with ants present or not
- when no external seed predators more fruits even if nectaries removed
- the ants chase off the predators
what is the acacia drepanolobium domatia example ?
- protected from large herbivores by ants
- ants provided with refuges in form of domatia and carbohydrates from EFN
- loss of large herbivores changes ant community
- mutualistic basis of symbiosis maintained by presence of large herbivores and in absence plant downregulates nectar secretion and domatia production
in Palmer et al 2008 study what did do/find and what were the 4 ant species studied and how do they vary?
exclude or keep large herbivores
- less herbivores less active nectaries and less swollen thorns
- loss of large herbivores can cause changes in ant community
- C.mimosae, C.siostedti, C.nigriceps, T.penzia
- vary in their defence of host trees and use of host tree rewards
in Palmer et al 2008 study what species was found to be a good and poor defender when looking at proportion of trees occupied?
C.s poor- when no large herbivores increase in ants
C.m good defender- when no herbivore reduction in trees occupied by ants as rely on tree for rewards
in Palmer et al 2008 study what are trees colonised by poor defender like?
higher mortality rate and low growth rate
in Palmer et al 2008 study what does the facilitation of highly destructive tree-boring insects by C.s provide?
mechanism for negative impact of ant on tree growth and survival
what did Huxley find about the relationship between ant plants Hydnophytum and Myrmecodia and ants? (3)
- plants produce specialized multi chambered tubers as refugia for ants
- swollen bottom part of stem full of interconnected chambers with lots of air flow and nesting area
- ants defend host and defecate in tubers which provides host with mineral nutrients (important for epiphyte as nutrients hard to find)
what did Huxley 1978 find when looking at the provision of mineral nutrients to the ant plant by ant faeces deposition inside tubers?
- made plants radioactive and measured this radioactivity in ants
- ant radiation detectable in plant and into shoots (suggesting plants are using the nutrients)
- ants spent the longest time in warted surface cavities full of microdebris
- the ants defecate more here (live elsewhere) as the warted surface has a higher SA so the plant can take up more nutrients
what is honeydew and why is it produced by aphids and what do ants do?
waste sugar produced as aphids need huge amounts of sugar for a small amount of nutrients
- attract bacteria and fungi which isn’t good
- ants farm the aphids by feeding on the honeydew and defending the aphids from predators
give 4 benefits of ant-aphid mutualism
- excess honeydew removed by ants, preventing fungal colonisation of sugar middens that could be fatal for the aphid
- ants defend immobile aphids from insect attack
- ants gain spatially and temporally stable carbohydrate and water source - ants protected aphid colonies more stable and persist longer
give 7 costs to ant plant mutualism
- presence of mutualistic ants can strongly affect persistence of aphid colonies or founding new colonies by dispersal
- ants can limit aphid dispersal
- ant adaptations limit winged aphid dispersal and benefit ants by allowing unusually crowded aphid aggregations so more honeydew produced
- winged dispersal isn’t the only way aphids colonise new plants
- when crowded condition late instar aphids will leave colonies to wander to new locations on the same plant or ground to new host
- presence of ants can produce tranquilising effects on aphids
in what 2 ways can ants limit aphid dispersal?
- direct physical manipulation (ants may bite or remove wings from aphids)
- chemical influence (mandibular secretions of ants can inhibit wing development)
give 3 points about how the presence of ants can have tranquilising effects on aphids
- limit motor functions
- attributable to direct contact with ants
- underpinned interspecific semiochemical communication
what did Oliver at al 2007 discover about the walking speed of aphids in the presence/absence of ants ?
reduction in walking speed at high aphid density when incontact with ants due to ant semiochemicals
- took a long time to reach the edge of the petri dish when exposed to ants
- ants almost in control of the symbiosis
what is pollination?
the transfer of pollen from anther to stigma of a carpel for the purpose of fertilising ovules
according to Bronstein et al 2006 what does preserved gymnosperm pollen in insect guts provide evidence for?
that insects were consuming pollen as far back as permian, before the angiosperm evolution in the late jurassic
according to Bronstein et al 2006 why did excess pollen likely evolve and when did nectar likely evolve and how can this be inferred?
excess pollen- first reward for early insect mutualists by late palaeozoic
nectar- before late jurassic, inferred from evolution of specialised nectar sucking mouthparts in diptera
what were early angiosperms and insects likely to be like?
generalised pollinators
insects lacked adaptations for flower feeding
what is an example of an honest signal used by flowers as a signal of quality?
fluctuating asymmetry
what is fluctuating asymmetry and what is it a measure of?
small random deviations from bilateral/radial symmetry
measure of phenotypic quality of individuals indicating ability of controlled development under given environmental and genetic conditions
what do nocturnal insects use to find the host?
perfumes or other odor based signals
what did Moller 1995 discover and measure when studying floral asymmetry?
tested if floral symmetry reliability reflects phenotypic quality measured in terms of pollinator rewards and if pollinators respond to the symmetry
- lower nectar with increasing asymmetry
- symmetrical flowers produce more nectar/reward
- strong relationship between degree of symmetry and number of visitations
what is an example of a deceptive signal and a plant that does this?
highly symmetrical but not producing much nectar
- bee orchid
- produces no nectar
- lures male bees by producing scents mimicking insect sex pheromones and acting as male morphological mimic
what did Oliver at al 2007 discover about how ants often limit aphid dispersal?
by removing wings and chemical manipulation of wing development pathway
what did Oliver at al 2007 discover for how the ant manipulation of aphid walking speed and dispersal can be detrimental or beneficial?
detrimental to aphid: if aphid dispersal used to reduce competition
beneficial: if dispersal used as enemy escape
